The weekends of the 3,4 and 10,11 of February witnessed 40 keen folk being introduced to, or refreshed on, winter tree ID and more will follow before the month ends. It might have been cold, and it certainly was wet on the first training day, but it was good to be out in the field again looking at flora, big and not so big. Once it warms up more we will lose the chance to identify trees on the many features available to see in the winter months.

Two common, native, deciduous trees are a good starting point for beginners; the mighty ash and magnificent oak. It might not look a very promising prospect, but there is much to observe and check against published guides.

OakAsh

Both trees pictured are ‘boundary trees’, so have been able to grow without hindrance, but both show storm damage and the ash, Fraxinus excelsior, is suffering from ash heart disease (but is clear yet of ash die-back). This oak is an English oak, Quercus robur – more easily identified in early autumn from the shape of its leaves and acorns hanging from a stalk (peduncle) – hence the other vernacular name for it, pedunculate oak.

We identified ash mostly from its twigs; dull black Bishop’s mitre shaped buds, single terminal bud, opposite lateral buds which twist at 90° along the twig (decussate), ash-grey twigs that tend to curve upwards towards the tip, somewhat flattened, smooth, hairless and with small warts (lenticels). Bark is smooth when young, becoming lightly fissured with age. Looking at the whole tree, we could see bunches of single keys (fruit) on some trees – these are females, trees without fruit may not have been productive last year, or may be males. Ash is dioecious – it has separate female and male trees. This tree is also well covered with ivy, Hedera helix, a common feature of ash.

We found English oak, Quercus robur (also know as navy oak because of the use of its timber for Elizabethan ships) but not Quercus patrea, sessile oak – a species more common to the west of County Durham. The latter has acorns directly on the stem (sessile), ie without a peduncle. Its leaves have more lobes and a base that tapers to a short leaf stalk (Q. robur has 2 ear-shaped auricles at the leaf base and tends to lack a leaf stalk). Oak twigs have a tight cluster of terminal buds, lateral buds are arranged alternately along its length, the twigs seem to be knobbly and don’t turn upwards as much as ash.

We were not looking to identify any hybrids but Quercus x rosacea, is a possible find. We didn’t spot any more exotic oaks at Rainton Meadows or Low Barns, which is a sign of good management – or did we find turkey oak, Quercus cerris? It is an attractive tree but a non-native species that is more competitive than the native species and offers less bio-diversity (by comparison, Q.robur can host c300 species of flora and fauna). We didn’t see other non-native species either, so the reserves officers and volunteers have been very methodical in their removal of unwanted trees. Sycamore, Acer pseudoplantinus, is easy to identify by its opposite green buds with tiny fringed margins, generally smooth bark and paired fruit (keys or samara). We looked at twigs from lilac, Syringa vulgaris, instead tree and twigs from spindle, Euonymus europaea, trees planted in a council amenity area – both with opposite green buds, but very different in size and shape.

Oak belongs to the Fagacaea family, as do beech, Fagus sylvatica, and sweet chestnut, Castanea sativa. Both of the latter grow to large mature trees and very often are planted. Beech is renowned for having a bare understory – its leaves inhibit the growth of almost anything under its crown. Instead there is a carpet of very distinctive brown beech leaves, very slowly decaying. Beech buds are also very distinctive, looking like thin cigars or torpedoes. Also look out for similar trees but with a very conspicuous twisting, fluted trunk and much smaller torpedo-shaped buds. These are common in the south and most likely to have been planted in our patch – hornbeam, Carpinus betulus.

Hazel, Corylus avellana, still had a few leaves on from last year and were useful reminders of what to look for in a few months time when buds and catkins are no more. As the picture shows, hazel catkins are easy to see, well the male ones are. A sudden burst of yellow dust, pollen, flew off the catkins when flicked. Female catkins are less numerous, tiny, with short and slender pink styles protruding slightly from the bud.

Alder, Alnus glutinosa, tolerates wet conditions and is plentiful at both Visitor Centres. Like hazel, it bears male and female catkins at this time of year, but the female catkins are smaller. Female catkins from previous years remain on the tree for some time as larger, cone-shaped fruit. The buds are suitably described as ‘boxing gloves’, matt blue to grey/purple in colour.

Alder

It is a smaller tree than ash and oak, reaching less than 30m at most, but as this one shows it is an attractive tree.

There are plenty of birches on both reserves and we were looking to distinguish between silver birch (Betula pendula), downy birch (Betula pubescens) and any potential hybrids between the two. Again these trees were in flower, with the catkins rather shorter than on hazel. The narrow, upright form of the tree is a good clue, as is the peeling, silver bark on the thin trunks. Looking, and feeling, for white warts (lenticels) on the young twigs was the starting point and checking for short (downy) hairs next. As the sun was shining we could look at a twig towards the sun for a ‘halo effect’ – the hairs on downy birch show up nicely. We happily agreed that we had silver birch.

But hawthorn, Crataegus monogyna, and blackthorn, Prunus spinosa, offered a few problems when looking at longer twigs. Hawthorn has buds growing at the base of thorns (and when is a thorn a prickle or spine was cause for debate!) Blackthorn has buds along the thorns that tend to be very stout and decidedly nasty. At the base of the buds you can find a leaf scar – shaped like a broad cheesy grin (hawthorn) of a pinched ‘ooooo’ (blackthorn). You might have shrivelled reddish berries on the hawthorn (check the number of seeds inside – one for common hawthorn, two for the more southern species, midland hawthorn, Crataegus laevigata.

Hawthorn (left) Blackthorn (right)

We found a lone horse chestnut, Aesculus hippocastanum, with its fat sticky buds. There were plenty of willows to be seen, easy to spot with their spiralling buds, but with so many hybrids that can only be successfully separated by looking at different times of the year, we were happy to leave that challenge to another day.

We were using two excellent FSC guides;

Broad-leaved trees and shrubs in winter AIDGAP key (May & Panter)

Winter trees: a photographic guide to common trees and shrubs AIDGAP (Price & Bersweden) *** see below and the Collins Tree guide

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